Basically going for Rotten before Dragonslayer/Flexile saves about 15s (the running is faster mostly by not having to sit at the bonfire to change Lenigrats' location and not picking up the bone, the slower Rotten compensates the faster Dragonslayer/Flexile)

Going for +10 takes about 50s (Getting the 3 chunks + slab takes 30s, 2 warps take 15s and homeward after the 2 chunks on the ledge costs about 6s), saves about 25s by saving a Majula trip and not having to kill the Drangleic Lizard. You have a better weapon for 13 bosses, saving a good 25+ hits. In my estimations it's an average 30s timesave, so +10 saves only 5 seconds, but fights are a tiny bit more consistent.